Method of making beryllium-aluminum-magnesium-silicon wrought material

ABSTRACT

A method of producing wrought material containing beryllium, aluminum, magnesium and silicon comprising: forming a casting of said material in a mold having high thermal conductivity material; applying a protective metallic coating to said casting; heating the coated casting at a temperature of 700* to 1,050* F. for a period of 5 to 100 hours; extruding the heated casting at a rate of about 13 to 60 inches per minute; removing the jacket from the extruded casting; heating the extrusion at a temperature of 900* to 1,050* F. for a period of time of 12 hours to 1 week; and rolling the heated extrusion at a total reduction of 10 to 98 percent.

United States Patent Krock et al. 1 Apr. 25, 1972 54] METHOD OF MAKINGBERYLLIUM- 3,558,305 1/1971 Griffiths ..75/150ALUMINUM-MAGNESIUM-SILICON OTHER PUBLICATIONS WROUGHT MATERIAL Formingof Beryllium Metals Handbook, Eighth Edition,

[72] Inventors: Richard H. Krock, Weston; William J. Volume 4, pp. 405I969 Rlchmond, Reading, both of Mass.

[73] Assignee: P. R. Mallory & Co. Inc., lndianapolis, Exami'ier'fllohnCampbell [mi Assistant Examiner-Donald C. Reiley. lll

Attorney-Richard H. Childress, Robert F. Meyer and Henry [22] Filed:July 17, 1970 W. Cummings l. 5, 9 [2]] App 5 8 8 57 ABSTRACT [52] U S Cl29/527 29ll93 29/DIG 32 A method of producing wrought materialcontaining beryllizg/Dlc 47 164/76 um, aluminum, magnesium and siliconcomprising: forming a [51 Int Cl BZEik 19/00 ing of said material in amold having high thermal conduc- 58] Fie'ld DIG 47 tivity material;applying a protective metallic coating to said 4 casting; heating thecoated casting at a temperature of 700 to 1,050 F. for a period of 5 to100 hours; extruding the heated casting at a rate of about 13 to 60inches per minute; removing [56] References Cited the jacket from theextruded casting; heating the extrusion at a UNITED STATES PATENTStemperature of 900 to l,050 F. for a period of time of 12 hours to 1week; and rolling the heated'extrusion at a total 3,234,052 2/1966reduction of 10 to 98 percent. 3,30l,717 l/l967 3,349,597 10/1967 Gross..29/193 X 22 Claims, 5 Drawing Figures 4 14:1 5 l t 15 l2 :1 \14 l3 llIO PATENTED APR 2 5 1972 FIG 2 INVENTORS RICHARD H. KROCK WILLIAM J.RICHMOND FIG. 4'

ATTORNEY METHOD OF MAKING BERYLLIUM-ALUMINUM- MAGNESIUM-SILICONWROUGl-IT MATERIAL Previous attempts at preparing wrought products,sheet, plate, rod, bar made of beryllium-aluminum-magnesium-siliconalloy have not been successful on a commercial basis because of therelatively brittle nature of the alloy. This brittleness to date hasmade working the material very difficult.

In patent application, Ser. No. 873,635, filed Nov. 3, 1969, nowabandoned assigned to the same assignee as the present application aprocess of refining the microstructure is disclosed involving formingcastings of beryllium-aluminum alloys, and attaching the castings to anelectrode; partly melting the electrode while rotating the same, therebycausing droplets to fly from the electrode; and cooling the droplets toform particulate beryllium-aluminum material with a fine grainstructure.

While this process is successful in refining the grain structure andreducing the brittle nature of the material, the formation of wroughtproducts by rolling or extruding has still been difficult even with thisrefined grain structure.

It is an object of the present invention to provide wrought productsfrom beryllium-aluminum material.

It is the object of the present invention to provide a process forproviding beryllium-aluminum sheet material.

It is the object of the present invention to provide a process forproviding beryllium-aluminum plate material.

It is the object of the present invention to provide a process forproviding beryllium-aluminum rod material.

It is the object of the present invention to provide a process forproviding beryllium-aluminum bar material.

It is another object of the present invention to provideberyllium-aluminum wrought material with increased elongation.

It is another object of the present invention to provideberyllium-aluminum wrought material which has substantially the sameproperties in in transverse direction as in the longitudinal direction.

It is another object of the present invention to provide a process whichdoes not require the use of an intermediate matrix refinement step.

It is another object of the present invention to provide a process whichis suited to commercial use on conventional equipment.

Other objects will be apparent from the following description anddrawings.

FIG. 1 is a sectional view and FIG. 2 an end view of an evacuationjacket which can be utilized in the present invention.

FIG. 3 is a front view, FIG. 4 a top view, and FIG. 5 a side view ofextrusion dies which may be utilized in the present invention.

The alloy composition to be utilized in accordance with the presentinvention consists essentially of beryllium in an amount of about 60 toabout 85 percent by weight; aluminum about 14 to about 40 percent,magnesium about 0.1 to 5 percent and silicon about 0.1 to 5 percent byweight. Impurities are preferably each not greater than about 0.1percent; total not greater than about 1 percent.

The preferred composition consists essentially of about 70 to about 80percent by weight beryllium and 20 to about 30 percent by weightaluminum and about 0.2 to about 0.5 percent by weight each of magnesiumand silicon.

The first step in the process is to form castings of this alloycomposition. The method of casting may involve the use of an alkali oralkaline earth halide flux as described in application, Ser. No.667,910, filed Sept. 15, 1967, now U.S. Pat. No. 3,558,305.Alternatively, the casting may be formed in accordance with application,Ser. No. 832,439, filed June 11, 1969 now U.S. Pat. No. 3,548,915,wherein the melting chamber is first evacuated and then back filled withan inert gas prior to casting. Both of these applications as well as thesaid application, Ser. No. 873,635 are hereby incorporated into thepresent application by reference and expressly made a part hereof.

A third method of forming the casting is to form a a casting in theshape of a consumable electrode by any known method, for instance byeither of the methods as described in said U.S. Pat. No. 3,558,305 orU.S. Pat. No. 3,548,915 and then use this casting as a consumable arcelectrode in a consumable arc casting process. In consumable arc castinga DC voltage is employed between the consumable electrode and thecasting and an arc is struck therebetween. For example, the voltageutilized is from about 40 to about volts, and the current about 400 to800 amps. The mold must be made of a material which is highly thermallyand electrically conductive. Non-limiting examples of such materials arecopper and copper alloys and graphite. Copper and copper alloys arepreferred.

In the event that the casting process is carried out according to U.S.Pat. No. 3,558,305 and/0r U.S. Pat. No. 3,548,915, the preferred moldmaterial is a highly thermally conductive material. Among the moldmaterials which may be used are: graphite, copper, or copper alloys,iron or steel.

In general the mold will be liquid cooled, i.e., water cooled but aircooling may also be utilized where a less rapid cooling rate can betolerated. Air cooling usually results in a less fine microstructure incomparable casting section sizes. The smallest cross sectional dimensionin the casting may be up to 6 inches and higher, but preferably thesmallest dimension is below about three inches.

The mold is preferably shaped so that the casting is of cylindricalshape. However, square and rectangular castings can also be utilized inthe process as well as eliptical and hyperbolic cross sections. Thecasting may be of any desired length; however, for casting conveniencethe casting is usually not longer than 6 feet.

The next step is to clean up the castings to remove surfaceimperfections in the castings. This is preferably done by machining forexample on a conventional lathe having a conventional machining tool,i.e., tungsten carbide/cobalt. Machining lathes of this type areconventional and the lathe per se and its cutting tool form no part ofthis invention. The machining operation also is utilized to get thecastings to tolerances as close to the desired shape as practical.Exemplary dimensional tolerances are i 3 to i 10 thousandths. If thecasting is sufficiently close to tolerance and sufficiently free ofsurface imperfections the machining step may be eliminated.

After the machining operation a layer of protective metal is applied tothe casting. This material must have high thermal conductivity; besufficiently strong to withstand extrusion pressures and sufficientlyductile to flow. A relatively high melting point about l,000 C. ispreferred. Silver and gold and their alloys may be used but copper andcopper alloys, i.e., brass, bronze, are preferred. This layer can beapplied by placing the castings in a jacket of protective metal or byapplying a coating of protective metal for example by plating. If thecasting is placed in a jacket, the jacket preferably is of slightlylarger size, for example of 10 to 20 thousandths of an inch larger.

In the event that a plating solution is employed conventional platingsolutions may be utilized for this purpose including for examplecyanide, sulphate, and halide as the negative ion in solution.

The preferred procedure is to place the casting in the metal jacket,preferably copper, having an evacuation tube. An exemplary constructionof this is shown in FIGS. 1 and 2.

The jacket and evacuation tube is designated generally as 10 andincludes a hollow can portion 11. One method of assembly includes firstaffixing end plate 12 to the can preferably by welding or brazing 13.Casting 5 is then placed therein. Front plate 14 having an opening 14ainto which evacuation tube 15 has previously been affixed is then put inplace, preferably by welding or brazing. The assembly 10 includingcasting jacket and evacuation tube is now ready for further processing.

The evacuation procedure is carried out at a temperature from 700 tol,050 F. for a period of time of 5 to 100 hours. This removes gaseousimpurities and makes the surface substantially free of such impurities.The evacuation tube is sealed off by heating the tube and then hammerwelding, or other appropriate sealing. Preferably the casting ismaintained under vacuum during sealing.

Alternatively, if desired, gaps can be left in the welds or brazes andthe evacuation tube dispensed with. However, the surface is not as freeof impurities according to this latter procedure;

In the event the metallic coating has been applied by plating, the hotevacuation step may be carried out in an evacuated chamber, oralternatively, it may be dispensed with, with some sacrifice inimpurities content of the surface.

If the facilities permit it, the preferred method after heating thecasting during hot evacuation is to move the hot casting with the copperjacket directly into the extrusion operation.

However many plants would not have the facilities to do this and if thisis the case, the casting may be cooled and stored. If this is the case,it should then be reheated to a temperature of 700 to l,050 F. prior toextrusion. As shown in FIGS. 3-5, the extrusion die 20 may be made ofconventional die materials, preferably known die steels. It ispreferably rectangular and comprises a body portion 21 and shapingsurfaces 22. These surfaces include radius curves 23 and an integralcone 24 for streamline flow.

The extrusion rate should be between 13 and 60 inches per minute with anamount of reduction of area of 8:1 to 24:1. In other words the ratio ofinlet diameter squared to outlet diameter squared should be from about 8to about 24. Similar principles would govern the design of dies of othercasting cross sections, such as square or rectangular.

After extrusion the metal jacket is removed from the casting. This maybe done byvarious means, for example, by machining, for example on aconventional lathe of the type described above, having a tungstencarbide/cobalt or other appropriate tool. A second method involvesremoving the metal coating by etching or pickling, for example byplacing the extrusion in an acid bath. Exemplary acids include nitric,sulphuric, halides, hydrochloric and mixtures thereof. Basic solutionsmay also be used, including solutions of sodium hydroxide, potassiumhydroxide, ammonia hydroxide, etc. Other pickling solutions will beapparent to those skilled in the art.

After jacket removal the casting is heated for a period of .12 hours to1 week or longer at a temperature of from 900 to 1,050 F. This heattreatment is desirable in order to relieve stresses induced duringextrusion and to achieve some microstructural uniformity. The heattreatment is preferably carried out in a vacuum or an inert gas such asargon, helium or nitrogen. However, it also may be carried out in air ifimpurity tolerances are not too high.

After heat treatment a rolling operation is carried out. Conventionalrolls will be utilized appropriately shaped to obtain the desiredproduct, i.e. plate or sheet, or bar or rod. The amount of reductionbefore annealing is about 20 to about SOpercent. Preferably the amountof reduction is from about 20 to 40 percent, before the first anneal. Areheat of 3 to 10 minutes to 900 to l,050 F. between each pass ispreferably carried out. During the rolling operation the rolls arepreferably at an elevated temperature, preferably at a temperature of250 to 350 F. The roll should be lubricated with a dry lubricant forexample a colloidal graphite suspension in an inert liquid carrier suchas DFG" sold by Miracle Powder Products Corp., Cleveland, 0. Rollingshould be carried out from 10 to 30 mils per pass for plate thicknessgreater than one-fourth of an inch and for sheet. For thin sheet this iscontinued until the product is 100 mils thick. For still thinner sheetreduction should be at a rate of 5 to percent; preferably 8 to 10percent. Similar adjustments should be made in processing bar (Diameterabout linch) and wire.

Next a heat treatment of 950 to 1050F is carried out for a period ofabout to 40 hours.

If a uniform texture is desired in sheet of plate, after the heattreatment unidirectional rolling across the extrusion directionsufficient to balance the texture is carried out. Cross rolling iscarried out with approximately a 90 directional change preferably beingcarried out with each pass. Between each pass there should be a reheatto a temperature of 950 to l,050 F. for about 3 to 10 minutes. However,there may be two and even three passes in one direction followed by anearly equal number of passes in a direction approximately with respectto the previous pass. Preferably the rolling is carried out at 90 changeevery pass. This treatment results in a balanced texture and a producthaving substantially uniform properties in either direction.

Sheet produced by this process may be 20 mils and thicker. Sheet andplate may be as wide and as long as equipment permits.

The resulting properties of this process include tensile strength of55,000 to 75,000 psi, yield strength 45,000 to 65,000 psi, andelongation of about 3 to 12 percent. With appropriate cross rolling ofsheet and plate these properties are obtained in the transversedirection as well as the longitudinal so that the product issubstantially of a balanced texture.

We claim:

1. A method of producing wrought material containing beryllium,aluminum, magnesium and silicon comprising:

forming a casting of said material in a mold having high thermalconductivity material;

applying a protective metallic coating to said casting;

heating the coated casting at a temperature of 700 to 1,050 F. for aperiod of 5 to hours;

extruding the heated casting at a rate of about 13 to 60 inches perminute;

removing the jacket from the extruded casting;

heating the extrusion at a temperature of 900 to 1,050 F.

for a period of time of 12 hours to 1 week; and

rolling the heated extrusion at a total reduction of 10 to 98 percent.

2. A method according to claim 1 in which the extrusion is heatedbetween passes during rolling.

3. A method according to claim 1 including treating said casting toremove surface imperfections and/or obtain desired shape before applyingsaid protective coating.

4. A method according to claim 3 in which the treating operation iscarried out by machining.

5. A method according to claim 1 in which coating is applied by placingsaid casting in a jacket.

6. A method according to claim 5 in which said jacket has an evacuationtube and said casting is evacuated during a heating step.

7. A method according to claim 1 in which the amount of reduction ofarea during extruding is from 8 to 24.

8. A method according to claim 1 in which said jacket is removed bymachining.

9. A method according to claim 1 in which said jacket is removed byetching.

10. A method according to claim 1 in which the heating step prior torolling is carried out in an inert atmosphere.

11. A method according to claim 1 in which the heating prior to rollingis carried out in a vacuum.

12. A method according to claim 1 in which the rolling step is carriedout on heated rolls.

13. A method according to claim 1 in which during rolling the materialis reheated between passes.

14. A method according to claim 12 in which the amount of reductionduring rolling is 10 to 30 mils.

15. A method according to claim 12 in which the rolls are heated to atemperature of 250 to 350 F.

16. A method according to claim 1 in which rolling is also carried outin the transverse direction.

17. A method according to claim 1 in which below 100 mils reductions of5 to 10 mils are taken during rolling.

18. A method according to claim 16 in which a balanced texture productis obtained.

19. A method according to claim 17 in which the wrought product obtainedis sheet.

20. A method according to claim 1 in which the wrought product obtainedis plate.

21. A method according to claim 1 in which the wrought product obtainedis bar.

22. A method according to claim 1 in which the wrought product obtainedis rod.

2. A method according to claim 1 in which the extrusion is heated between passes during rolling.
 3. A method according to claim 1 including treating said casting to remove surface imperfections and/or obtain desired shape before applying said protective coating.
 4. A method according to claim 3 in which the treating operation is carried out by machining.
 5. A method according to claim 1 in which coating is applied by placing said casting in a jacket.
 6. A method according to claim 5 in which said jacket has an evacuation tube and said casting is evacuated during a heating step.
 7. A method according to claim 1 in which the amount of reduction of area during extruding is from 8 to
 24. 8. A method according to claim 1 in which said jacket is removed by machining.
 9. A method according to claim 1 in which said jacket is removed by etching.
 10. A method according to claim 1 in which the heating step prior to rolling is carried out in an inert atmosphere.
 11. A method according to claim 1 in which the heating prior to rolling is carried out in a vacuum.
 12. A method according to claim 1 in which the rolling step is carried out on heated rolls.
 13. A method according to claim 1 in which during rolling the material is reheated between passes.
 14. A method according to claim 12 in which the amount of reduction during rolling is 10 to 30 mils.
 15. A method according to claim 12 in which the rolls are heated to a temperature of 250* to 350* F.
 16. A method according to claim 1 in which rolling is also carried out in the transverse direction.
 17. A method according to claim 1 in which below 100 mils reductions of 5 to 10 mils are taken during rolling.
 18. A method according to claim 16 in which a balanced texture product is obtained.
 19. A method according to claim 17 in which the wrought product obtained is sheet.
 20. A method according to claim 1 in which the wrought product obtained is plate.
 21. A method according to claim 1 in which the wrought product obtained is bar.
 22. A method according to claim 1 in which the wrought product obtained is rod. 